Energy efficiency outfit Ameresco announced on Wednesday the completion of a 4.3-megawatt biogas energy recovery facility in Dallas, Texas.

The new plant will generate electricity and thermal load to power facilities operated by Dallas Water Utilities, and is expected to offset 60 percent of the electricity DWU draws from the grid, saving the city about $1.5 million each year.

In a nutshell, the facility captures waste heat from the wastewater treatment process and creates energy from about 80 percent of it. Currently, the DWU can treat up to 110 million gallons of wastewater each day -- but excess gas at the facility is usually burned off by flares.

The idea is to try to close that loop. Ameresco says that it can treat and deliver up to 1,200 standard cubic feet of biogas per minute, reducing carbon emissions by the equivalent of about 3,500 cars each year.

This methane capture technology is usually seen at landfills, but it's starting to make headway in other municipal service areas.

Dallas isn't the first utility to recycle biogas into energy, but it's among the earliest. The first such sewage facility in the U.S., in state rival San Antonio, went online in September 2010.

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